Question

an object kept 60cm from a lens gives a virtual image 20cm in front of lens.what is the focal length of lens?is it a converging or diverging lens?​

Answer 1

Given,

Onject distance, u = - 60 cm

image distance, v = - 20 cm

Focal length, f = ?

Now, using the lens formula,

1/f = 1/v - 1/u

= 1/(-20) - 1/ (-60)

= 1/60 - 1/20

= 1 - 3 / 60

= - 2/ 60

i.e., focal length, f = - 30 cm

Hence, the lens is a diverging less with focal length of 30 cm.

HOPE! IT HELPS YOU

PLEASE MARK AS BRAINLIST

Answer 2

1/f = 1/v - 1/u

u = -60 cm

v = -20 cm

substituting values u get f= -30cm

which implies its a diverging or concave lens